The present invention can be suitably applied to a storage system including a storage apparatus for providing a dynamically capacity-extensible logical volume to a host computer.
In recent years, a storage apparatus for providing a data storage extent to a host computer can be equipped with a considerable number of large-capacity physical disks, and the storage capacity is being increased on a grand scale. With this kind of storage apparatus, foremost, a disk array configured from RAID (Redundant Array of Independent Disks) is created from physical disks, a plurality of physical storage resources are gathered to create a pool area, and a storage extent of a capacity requested by a host computer from the pool area is created as a logical volume and provided to the host computer.
Further in recent years, a storage apparatus has been proposed for dynamically extending the storage capacity by foremost providing a virtual logical volume to the host computer without creating a logical volume of a fixed capacity from the pool area, and dynamically allocating a storage extent in certain units from a pool area as a physical resource to such virtual logical volume according to a command from the host computer.
For instance, with the storage apparatus of Japanese Patent Laid-Open Publication No. 2003-015915 (Patent Document 1), a logical volume corresponding to the individual host computers is provided from a plurality of disk storage apparatuses, a logical block address subject to reading or writing is read based on a command to a logical volume sent from a host computer, a volume providing apparatus allocates a storage extent from an unused magnetic disk storage apparatus when a storage extent of the logical block address accessed by the command does not exist in the logical volume, the storage extent of the logical volume is dynamically extended, and the logical volume is reduced in an arbitrary amount based on the command of the application.
Further, the storage apparatus of Japanese Patent Laid-Open Publication No. 2005-011316 (Patent Document 2) has a storage controller connected to a host computer, and a plurality of storage apparatuses connected to the storage controller, wherein the storage controller issues a notice to the host computer to the effect that a virtual volume of a prescribed size has been allocated according to a command from, the host computer, allocates the storage extent existing in the plurality of storage apparatuses to the virtual volume upon receiving from the host computer a command to the virtual volume, converting the command received from the host computer into a command addressed to the storage apparatus having the storage extent to which the virtual volume was allocated, and sending the converted command to this storage apparatus.
Nevertheless, with the storage apparatus of Patent Document 1, although it describes that the unnecessary storage extent arising as a result of reducing the size of the file system in the host computer is released from the volume, it does not describe releasing the unnecessary storage extent arising as a result of deleting data of files and the like that are written in the storage extent discontinuously from the volume, and it is possible that unnecessary storage extents will remain in the volume.
Further, with the storage apparatus of Patent Document 2, it describes releasing the unnecessary storage extent by the storage controller monitoring the commands and, upon updating the metadata of the file system pursuant to the deletion of data of files and the like described above, releasing the storage extent indicated by such metadata. Nevertheless, there is a problem in that the configuration of the storage controller will become complex since the storage controller needs to constantly monitor the file system and perform processing according to the file system in correspondence to a broad range of operation systems and file systems of the host computer.